Radii



at least 45.

United States Patent O l 3,126,437 GAUSSIAN PHOTOGRAPHIC OBJECTIVE Lena M. Hudson, Brighton, and `Iohn M. Schwartz,

Irondequoit, N.Y., assignors to Bausch & Lomb Incorporated, Rochester, N.Y., a corporation of New York Filed Dec. 27, 1960, Ser. No. 78,594

2 Claims. (Cl. 88-57) The present invention relates generally to 'a photographic objective for use in taking or projec-ting pictures or similar use, and relates more particularly to improvements in a so-called Gauss type of objective. v

A prime objective of this invention is to provide a novel and improved Gauss type of photographic objective of at least ,f/ 1.8 relative aperture and at least 45 field angle wherein the chromatic and spherical aberrations, coma and astigmatism are particularly well corrected,` and wherein zero distortion has been achieved together with an excellent flat field. I-t is a further object of this invention to provide such a device having a relatively long back focus of at least .61F where F denotes the equivalent focus of the objective and the use of low curvatures in the lens surfaces thereof resulting in a lower cost of manufacture.

Further objects and advantages will be apparent in the arrangement of parts and details of( construction by reference to the specification herebelow taken together with the drawing wherein:

FIG. 1 is an optical diagram showing an optical system of the above-mentioned kind;

FIG. 2 is a chart of constructional data related to one form of the present invention;

FIG. -3 is a chart of constructional data related to a second form of the present invention; and

FIGS. 4, 5 and 6 are graphs which are plotted to show the excellent condition of spherical aberration, coma and astigmatism respectively, found in said optical system.

The present invention is exemplified in a Gauss type of photographic objective which is indicated generally by numeral in FIG. 1, said objective having a long back focus designated by BF, of at least .61F where F designates the equivalent focus of the objective 10 and having a relative aperture as large as f/ 1.8.

According to this invention, distinct improvements in the spherical and chromatic aberrations of the objective 10 are provided together with an excellent condition of coma, astigmatism and zero distortion. Additionally, a superior flat field is achieved over a total field angle of These advantageous features are obtained along with rela-tively flat lens surface curvatures which permit reduction in manufacturing costs, and particularly, thesefeatures are obtained by use of the most beneficial relationship for refractive index and Abbe number amongst the lens elements in said objective.

Said objective comprises two convex-concavo meniscus lens members 11 and 12 spaced from the front and the rear sides respectively, of an interposed diaphragm 13 in optical alignment with each other, said lens members being concave toward the diaphragm. Optically aligned therewith and spaced forwardly thereof is a collective singlet lens vinem-ber I, and rearwardly spaced from member 12 is a collective'single lens Vl which together form a compact objective having a relatively short overall length of not greater than .8F and having a long back focus of at least .6lF where F denotes the equivalent focus of said objective 10.

Lens member'll is composed of a positive plano convex lens element II and a negative plano concave ele` ment III which is preferably cemented thereto to form a plano interface R4, the curve refractive surfaces R3 and R5 thereof being concave toward the diaphragm 13.

3,126,431. Patented Mar. 24, 1964 ICC Lens member 12 is composed of a positive meniscus lens element V located rearwardly of and preferably in cemented contact with a negative meniscus lens element IV along an interface R7 therebetween.

In this invention, the refractive index of the glasses in the various lens elements I to VI is generally high and the various chosen values of nD and v are so distributed and sequentially arranged as to achieve a particularly fine correction for astigmatism as well as coma, spherical and chromatic aberrations and distortion as well as field flatness.

In FIG. 4 -is shown the excellent condition of spherical aberration for the D line of the spec-trum which is shown as a solid line and Ifor the G' line ofthe spectrum which is shown'as a .dot-ted line.

In FIG. 6 the sagittal astigmatism is designated by S and the tangential astigmatism -is designated by T.

The most favorable range of nn and u values forobtaining the aforesaid optical properties is given in Table I herebelow.

Table I Elem. I

nD Elem. II

Elem. III

i 'up (Elem. II)=nD (ElemQIII) nl): (Elem. IV) nD= (Elem. V)

nn( Elem. IV) '92 nD( E1em. I)

3.1 v(Elem. I)-v(Elem. II) 6.0 12.0 v(Elem. II)-11(Elem. III) 13.5 9.0 v(Elem. I) -z/(Elem. IV) 16.0 1.5 1(Elem. V) y(Elem. I) 10.2 1.4 u(Elem. VI) y(Elem. I) 7.8v

Table Il .96 substantially A series of photographic objectives of a distinctive form following the teachings of this invention have been constructed using the restricted ranges of constructional data given herebelow in Table III, the notation used therein being the same as found in Tables I and II.

Table III One successful form of the aforesaid ser-ies isdescribed in detail with respect to its constructional properties which appear in Table IV herebelow and also appear in FIG. 2 of the drawing wherein the notations I to VI denote the individual lens elements, R1 to R10 denote the radii of the refractive surfaces, t1 to t6 denote the axial thicknesses of the lenses, S1 to S4 denote the axial airl spaces between the lens'members, nn denotes the refractive index, and v represents the Abbe number of the glass used in the respective lens elements, and FA denotes the eld angle.

, The specic constructional data for a second form of the invention is given in Table V herebelow and is shown 4 in FIG. 3 of the drawing, wherein the various notations have the same meaning as in the foregoing tables.

It will be understood that -although only two forms of this invention have been shown and described in detail, other forms are possi-ble and changes may be made in the details thereof without departing from the spirit of the invention as defined in the claims herebelow.

What is claimed is:

1. A Gauss type of photographic objective which is well corrected for spherical and chromatic aberrations, astigmatism, comafatness of eld and distortion and having a long back focus of substantially .62F where F denotes the focal length .of said objectives, a eld angle of at least 45, and a short overall length of less than .8F, said objective comprising two negative meniscus lens mem-bers which are located in optical alignment and in spaced relation to each other and between two.outer collective single lens members, said meniscus members lbeing concave towards an interposed diaphragm and each said meniscus member being composed of a negative and a positive lens element with the negative elements being closest to each other, the constructional data for said objective `being given in the statements of inequalities herebelow wherein R1 to Rm' denote the radii of the lens surfaces, t1 to t6 denote the axial thicknesses of the successive lens elemen-ts numbering from the front of the vobjective, S1 to S4 denote the axial air spaces between the lens members, nD denotes the refractive index, and u denotesthe Abbe number of the glass from which the various lens elements are made,

5 6 2. A Gauss type of photographic objective which is [E,F=100, B,F.=63.38 F-A.=45 L81 well corrected for spherical and chromatic aberrations,

astigmatism, coma, atnessof eld and distortion and hav- Lens Radii Thieknesses Spaeings D y ing a long back focus of substantially .62F where F denotes the focal length of said objective, a eld angle of 5 Ri=75-46 v 45.5 at least 45, and a short overall length of less than .8F, I 11F-273.87 t1=9.01 1,744 vsaid objective comprising two negative meniscus lens R3=4Z52 S1=010 members which are located in optical alignment arid in H t,=16,55 1,720 420 spaced relation to each other and between two outer col- 10 m R4= 32200. 1 m

lective single lens members, said meniscus members being Rs=28.19 29's concave toward an interposed diaphragm and each said Sigg? meniscus member being composed of a negative and a .Y IV R=-3290 t 7 01 1 positive lens element with the negative elements being R1=m 4"' '689 309 jective being given in the statements of inequalities here- S4=0.1o

below wherein R1 to R10 denote the radii of the lens sur- VI R=250-96 F892 1.720 47.5

faces, t1 to te denote the axial thicknesses of the succes- RIF-10945 sive lens elements numbering from the front of the objective, S1 to S4 denote the ax-ial air spaces between the lens 20 References Cited in the file 0f this Patentmembers, nD denotes the refractive index, and v denotes UNITED STATES PATENTS the Abbe number of the glass from which the various 2,735,340 Aklin Feb 21, 1956 le elements are made 2,784,643 Brendel et a1 Mar. 12, 19-57 25 FOREIGN PATENTS 210,640 Austria Aug. 10, 1960 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No., 3, 126,437 March 24, 1964 Lena Mn Hudson et Rle lt is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column l, line 7l, for Hcurve" read curved column 4, line. 37, for "objectives" read objective f; line 42, for single read w singlet line 43, for "towards" read u toward m; column 5, line lO, for "single read singlet se; column 6, in the table, under the heading "v"line l, thereof, :for "4595"" read 45,6

Signed and sealed this 21st day of July 1964 (SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attestng Officer Commissioner of Patents 

1. A GAUSS TYPE OF PHOTOGRAPHIC OBJECTIVE WHICH IS WELL CORRECTED FOR SPHERICAL AND CHROMATIC ABERRATIONS, ASTIGMATISM, COMA, FLATNESS OF FIELD AND DISTORTION AND HAVING A LONG BACK FOCUS OF SUBSTANTIALLY .62F WHERE F DENOTES THE FOCAL LENGTH OF SAID OBJECTIVES, A FIELD ANGLE OF AT LEAST 45*, AND A SHORT OVERALL LENGTH OF LESS THAN .8F, SAID OBJECTIVE COMPRISING TWO NEGATIVE MENISCUS LENS MEMBERS WHICH ARE LOCATED IN OPTICAL ALIGNMENT AND IN SPACED RELATION TO EACH OTHER AND BETWEEN TWO OUTER COLLECTIVE SINGLE LENS MEMBERS, SAID MENISCUS MEMBERS BEING CONCAVE TOWARDS AN INTERPOSED DIAPHRAGM AND EACH SAID MENISCUS MEMBER BEING COMPOSED OF A NEGATIVE AND A POSITIVE LENS ELEMENT WITH THE NEGATIVE ELEMENTS BEING CLOSEST TO EACH OTHER, THE CONSTRUCTIONAL DATA FOR SAID OBJECTIVE BEING GIVEN IN THE STATEMENTS OF INEQUALITIES HEREBELOW WHEREIN R1 TO R10 DENOTE THE RADII OF THE LENS SURFACES, T1 TO T6 DENOTE THE AXIAL THICKNESSES OF THE SUCCESSIVE LENS ELEMENTS NUMBERING FROM THE FRONT OF THE OBJECTIVE, S1 TO S4 DENOTE THE AXIAL AIR SPACES BETWEEN THE LENS MEMBERS, ND DENOTES THE REFRACTIVE INDEX, AND V DENOTES THE ABBE NUMBER OF THE GLASS FROM WHICH THE VARIOUS LENS ELEMENTS ARE MADE, 